Underwater power plant having removable nacelle

ABSTRACT

The invention relates to an underwater powerplant, comprising
         a support structure;   a nacelle, the support structure and the nacelle being detachably connectable to one another via a coupling device;   a water turbine, which at least indirectly drives an electrical generator, which is received in the nacelle;   characterized in that   the underwater powerplant further comprises an inductive transmission device, which transmits the power generated by the electrical generator from the nacelle in a contactless manner to the support structure.

The invention relates to an underwater powerplant having adisconnectable nacelle according to the preamble of the independentclaims, in particular for obtaining power from a tidal current.

Underwater power plants which are implemented without a dam structureand having free flow around them, and are used for obtaining energy froma tidal current, are known. Such freestanding plants can also be usedfor flowing bodies of water. For such plants, a water turbine driven bythe current flows around the nacelle and drives an electrical generatorhoused inside the nacelle at least indirectly. The nacelle is mounted ona support structure, which can either be placed on a foundation on thebody of water floor or can be implemented as a floating unit. Themounting of the nacelle on the support structure can be implemented asrigid. Alternatively, the nacelle is fastened on the support structureso it is rotatable in such a way that tracking of the water turbine ispossible in the case of a varying inflow direction.

To execute a plant service and to simplify the installation, a modularlyconstructed underwater powerplant has been proposed by EP 1 366 287 A1,for example. A foundation is first erected from individual components onthe body of water floor, having a support structure constructed thereon.The nacelle is subsequently lowered along a guide cable configuration tothe support structure. A connection cable, which originates from theelectrical generator or the power-electronic components in the nacelle,is laid by service divers in a guide channel on the support structure.This type of installation is complex and hazardous because of the use ofthe service divers. Further raising of the nacelle to execute a plantservice above water proves to be correspondingly difficult.

To simplify the cable guiding, it was proposed by GB 2 437 534 A for amodular underwater powerplant that a rigid pipe connecting piece be usedon the nacelle, which receives and protects a first portion of theconnection cable. The constructive outlay for implementing theconnecting piece is a disadvantage in such a design. In addition, thisplant part interferes with the handling of the nacelle. This relates tothe initial installation and to maintenance work, which is executed onboard a water vehicle. For this case, the connecting piece protrudingfrom the housing of the nacelle will result in a correspondinglylarge-dimensioned crane and handling system onboard the water vehicle.

A connection cable which is external after the plant installationrepresents a component which is susceptible to wear because of thecontinuous movement due to the surrounding current. These fatigueproblems cannot be entirely overcome even by components of a cableprotection system which are attached in segments. In addition, the cablelocated in the current can result in vibrations. Furthermore, afastening on the support structure is to be provided, which ensures asufficient distance from the orbit of the water turbine duringoperation. This is complex.

Further problems of the known, modular underwater power plants result inthe case of a rotatable linkage of the nacelle to the support structureto track the water turbine in relation to a variable-direction inflow.For this case, excessively strong twisting of the connection cableoriginating from the nacelle is to be avoided. For actively motorizedazimuthal rotational devices, a continuous change of the rotationaldirection, in the simplest case a back-and-forth movement, can beexecuted to avoid these problems. However, passive azimuthal rotationdevices are preferred to simplify the system. To avoid the twisting forsuch a device, it was proposed by DE 10 2007 002 338 B3 that theazimuthal rotation be synchronized with the intrinsic rotation of acentrally running connection cable. However, this is connected with anadditional design effort for coupling the rotational movements of thenacelle and the connection cable.

The invention is based on the object of specifying a modular underwaterpowerplant having a nacelle which is removably fastened on a supportstructure, whose coupling and decoupling is simplified. In particular,the connection cable for transmitting the electrical power generated bythe electrical generator in the nacelle is to be reliably protectedduring installation and removal and during normal plant operation. For arefinement, the nacelle is to be able to execute a rotation around thesupport structure in the coupled state, in order to be able to follow adirection change for the inflow, without cable twisting being able tooccur.

To achieve the object, the inventors have recognized that a modularunderwater powerplant should transmit the electrical power generated bythe electrical generator in the nacelle inductively and accordingly in acontactless manner to the support structure. For this purpose, aninductive transmission device can be provided between the nacelle andthe water turbine, which is detachable and thus allows coupling anddecoupling of the nacelle to and from the support structure. Theinductive transmission device can be implemented by a transformer for afirst design. In the case of a directionally-rigid coupling of theunderwater powerplant to the support structure, a transformer can beused, whose primary side is assigned to the nacelle and whose secondaryside is assigned to the support structure. The use of a plurality ofsuch transformers is conceivable, which can be implemented as a part ofor in the area of the coupling device for connecting the nacelle to thesupport structure.

To implement an underwater powerplant having a nacelle linked so it isrotatable on the support structure, the inductive transmission deviceaccording to the invention is also designed having parts movablerotatably to one another. A preferred embodiment is the use of a rotarytransformer, which is implemented as an electrical generator, forexample, as an asynchronous machine having a wound rotor, which isfixedly braked.

An induction machine having a rotor feed to implement a rotarytransformer is particularly preferred.

An alternative embodiment of the invention provides implementing theelectrical generator, which is at least indirectly driven by the waterturbine in operation, as separable and to dispense with a separateinductive transmission device. The rotor of the electrical generator 6is assigned to the nacelle 2 and the stator of the electrical generator6 is assigned to the support structure. Accordingly, the electricalgenerator is implemented as separable and can correspondingly beassigned to the two halves of the coupling device. The two parts can beseparated or connected in the submerged state.

For installation, the support structure is first sunk with the generatorstator. In a subsequent installation step, the revolving unit having therotor is placed on the support structure, the coupling device allowingrenewed detachment and decoupling of the revolving unit. In the case ofa plant service, the revolving unit having the generator rotor is raisedto the water surface, while the generator stator remains in the supportstructure, since these plant components are to be viewed as essentiallymaintenance-free.

The above-mentioned embodiment of the invention having a separableelectrical generator is advantageously implemented having a flooded airgap. Furthermore, the bearing components are advantageously designed aswater-lubricated friction bearings, so that the revolving unit iscoupled to the initially exposed rotor of the electrical generatorunderwater. Furthermore, to simplify the coupling, complementary guideunits are provided on the revolving unit and the water turbine, whichcause self-centering.

The invention is described in greater detail hereafter on the basis ofexemplary embodiments in connection with illustrations in the figures.In the specific figures:

FIG. 1 shows a modularly constructed underwater powerplant according tothe invention, having a nacelle decoupled from the support structure.

FIG. 2 shows an underwater powerplant in longitudinal section for theembodiment alternative of the invention having a separable electricalgenerator.

FIG. 1 shows an underwater powerplant according to the invention inschematically simplified form. It is constructed modularly according tothe species and has a support structure 4, which is guided down to thebody of water floor 5 in the present case. A nacelle 2, which in turncarries a water turbine 3, can be coupled onto this support structure 4.For the present embodiment, an electrical generator 6 is additionallyreceived in the nacelle 2. This generator is at least indirectly drivenby the water turbine 3 and converts the kinetic energy absorbed from thecurrent into electrical power. A coupling device 15 is provided forcoupling the nacelle 2 on the support structure 4. For the illustratedexemplary embodiment, it comprises a receptacle 12 in the supportstructure 4 and a connecting piece 13, which is connected to the nacelle2. Receptacle 12 and connecting piece 13 have complementary guideelements 14 in the form of conical running surfaces for theself-centering. Further centering and locking means (not shown indetail) of the coupling device can be provided to implement a detachableconnection of the nacelle 2 to the support structure 4.

According to the invention, the modularly constructed underwaterpowerplant 1 has an inductive transmission device 7, which is used forthe purpose of transmitting the electrical power generated by theelectrical generator 6 in a contactless manner from the nacelle 2 to thesupport structure 4. For this purpose, the inductive transmission device7 can comprise a transformer 9, whose primary side 10 is assigned to thenacelle 2 and whose secondary side 11 is assigned to the supportstructure 4. The inductive transmission device 7 can be part of thecoupling device 15, as shown, or can be implemented in proximitythereto. Because of the self-centering of the coupling device 15 causedby the complementary guide elements 14, the partial components of thetransformer 9, which are guided toward one another during the coupling,can be precisely positioned to one another on the primary site 10 andthe secondary site 11. In this way, it is possible to reduce thedistance to be bridged in a contactless manner or to provide componentswhich interlock like teeth for the primary side 10 and the secondaryside 11, which improve the efficiency of the inductive powertransmission.

To implement a simple coupling ability, the inductive transmissiondevice 7 is implemented in such a way that its components areencapsulated in relation to the surrounding water, but the air gap areaof the electrical generator is flooded after the coupling.

A rotary transformer represents a possible embodiment for the inductivetransmission device 7, which is particularly used to implement arotatable mount for the nacelle 2 on the support structure. It can beimplemented as an asynchronous machine having a wound rotor, which isfixedly braked for a specific operating position. The fixing brake usedfor this purpose is preferably implemented so it can be disengaged, sothat an azimuthal rotation of the nacelle can be executed.Correspondingly, for this case, the primary side of the rotarytransformer moves in relation to the secondary side fixed on the supportstructure during tracking of the nacelle.

For the mentioned rotary transformer, the absolute value of thesecondary voltage is unchanged in relation to the primary voltage. Onlythe phasing is variable as a function of the rotational position. Therotary transformer is particularly preferably implemented as aninduction machine having rotor feed, whose components are protectedagainst the corrosive action of the surrounding water by a corrosionprotection element, such as a can, or using a casting compound, so thatoperation in the surrounding water is possible.

FIG. 2 shows an alternative embodiment of the invention, instead of aseparate inductive transmission device, the electrical generator 6itself representing the plant part to be coupled. Corresponding to theabove-described embodiment, there is a contactless coupling via amagnetic interaction. There is a higher efficiency in comparison to theabove-described embodiment, however, for this case the coupling betweenthe support structure 4 and the revolving unit 16 is to be implementedso precisely that the required air gap tolerances are implementable inthe millimeter range for the electrical generator.

In detail, FIG. 2 shows a modular underwater powerplant 1 inschematically simplified form, whose water turbine 3 is implemented as avertical rotor. The revolving part 16 carries, in addition to the waterturbine 3, the generator rotor 17, which advantageously comprisespermanent magnets. Furthermore, the revolving part carries the bearingsegments assigned thereto of the bearings 20, 21, and 23. The counterrunning surfaces of these bearings are connected to the supportstructure 4, which has a foundation on the body of water floor 5. Itreceives the generator stator 18 and the frequency inverter 24, fromwhich the connection cable 8 can be guided protected up to the placementlocation on the body of water floor 5.

Upon coupling of the revolving unit 16 to the support structure 4, aconical receptacle 12 in the support structure 4 is used for a firstcentering. Furthermore, a centering device 23 is provided on therevolving unit 16, which causes the final centering in the end phase ofthe coupling together with a complementarily shaped receptacle in thesupport structure 4. Furthermore, the diagonally placed bearing 22supports the self-centering, so that the required tolerances of the airgap 19 are maintained between the generator rotor 17 and the generatorstator 18. The air gap 19 and the areas in which the bearings 20, 21, 22are implemented are preferably flooded using surrounding water.Electrical components of the frequency inverter 24 and the electricallyconductive parts of the generator 6 are encapsulated.

LIST OF REFERENCE NUMERALS

-   1 underwater powerplant-   2 nacelle-   3 water turbine-   4 support structure-   5 body of water floor-   6 electrical generator-   7 inductive transmission device-   8 connection cable-   9 transformer-   10 primary side-   11 secondary side-   12 receptacle-   13 connecting piece-   14 complementary guide elements-   15 coupling device-   16 revolving part-   17 generator rotor-   18 generator stator-   19 air gap-   20 bearing-   21 bearing-   22 bearing-   23 centering device-   24 frequency inverter

1-9. (canceled)
 10. An underwater powerplant comprising: a supportstructure; a nacelle, the support structure and the nacelle beingdetachably connectable to one another via a coupling device; a waterturbine, which at least indirectly drives an electrical generator, whichis received in the nacelle; characterized in that the underwaterpowerplant further comprises an inductive transmission device, whichtransmits power generated by the electrical generator from the nacellein a contactless manner to the support structure.
 11. The underwaterpowerplant according to claim 10, characterized in that the inductivetransmission device comprises a transformer, whose primary side isconnected to the nacelle and whose secondary side is connected to thesupport structure.
 12. The underwater powerplant according to claim 11,characterized in that the transformer is implemented as a rotarytransformer.
 13. The underwater powerplant according to claim 12,characterized in that the rotary transformer is implemented as aninduction machine having rotor feed, the rotor forming the primary sideof the transformer and being fixedly braked in relation to the stator ofthe induction machine after the connection of the nacelle and thesupport structure.
 14. The underwater powerplant according to claim 10,characterized in that complementary guide elements are provided on thenacelle and the support structure, which cause self-centering during theconnection of the nacelle and the support structure.
 15. The underwaterpowerplant according to claim 11, characterized in that complementaryguide elements are provided on the nacelle and the support structure,which cause self-centering during the connection of the nacelle and thesupport structure.
 16. The underwater powerplant according to claim 12,characterized in that complementary guide elements are provided on thenacelle and the support structure, which cause self-centering during theconnection of the nacelle and the support structure.
 17. The underwaterpowerplant according to claim 13, characterized in that complementaryguide elements are provided on the nacelle and the support structure,which cause self-centering during the connection of the nacelle and thesupport structure.
 18. The underwater powerplant according to claim 14,characterized in that the complementary guide elements comprise aconical connecting piece on the nacelle and a conical receptacle on thesupport structure.
 19. The underwater powerplant according to claim 15,characterized in that the complementary guide elements comprise aconical connecting piece on the nacelle and a conical receptacle on thesupport structure.
 20. The underwater powerplant according to claim 16,characterized in that the complementary guide elements comprise aconical connecting piece on the nacelle and a conical receptacle on thesupport structure.
 21. The underwater powerplant according to claim 17,characterized in that the complementary guide elements comprise aconical connecting piece on the nacelle and a conical receptacle on thesupport structure.
 22. The underwater powerplant according to claim 13,characterized in that the inductive transmission device is implementedon the surfaces of the complementary guide elements facing toward oneanother.
 23. The underwater powerplant according to claim 14,characterized in that the inductive transmission device is implementedon the surfaces of the complementary guide elements facing toward oneanother.
 24. The underwater powerplant according to claim 10,characterized in that the support structure is supported against a bodyof water floor.
 25. The underwater powerplant according to claim 11,characterized in that the support structure is supported against a bodyof water floor.
 26. The underwater powerplant according to claim 12,characterized in that the support structure is supported against a bodyof water floor.
 27. The underwater powerplant according to claim 13,characterized in that the support structure is supported against a bodyof water floor.
 28. The underwater powerplant according to claim 14,characterized in that the support structure is supported against a bodyof water floor.
 29. An underwater powerplant comprising: a supportstructure for supporting the underwater powerplant on the body of waterfloor; a revolving unit, the support structure and the revolving unitbeing detachably connectable to one another via a coupling device whichcan be actuated in the immersed state; a revolving water turbine, whichis at least indirectly connected to the revolving unit; characterized inthat: the electrical generator is implemented as separable, thegenerator rotor being assigned to the nacelle and the generator statorbeing assigned to the support structure.